Biocidal compositions and use thereof

ABSTRACT

A microbial inhibiting composition and method is disclosed. The composition comprises an amount, effective for the intended purpose of diiodomethyl-p-tolylsulfone and dodecylguanidine hydrochloride. The method comprises administering an amount of this combined treatment to the particular water containing system for which treatment is desired.

BACKGROUND OF THE INVENTION

The formation of slimes by microorganisms is a problem that isencountered in many aqueous systems. For example, the problem is notonly found in natural waters such as lagoons, lakes, ponds, etc., andconfined waters as in pools, but also in such industrial systems ascooling water systems, air washer systems and pulp and paper millsystems. All possess conditions which are conducive to the growth andreproduction of slime-forming microorganisms. In both once-through andrecirculating cooling systems, for example, which employ largequantities of water as a cooling medium, the formation of slime bymicroorganisms is an extensive and constant problem.

Airborne organisms are readily entrained in the water from coolingtowers and find this warm medium an ideal environment for growth andmultiplication. Aerobic and heliotropic organisms flourish on the towerproper while other organisms colonize and grow in such areas as thetower sump and the piping and passages of the cooling system. The slimeformation not only aids in the deterioration of the tower structure inthe case of wooden towers, but also promotes corrosion when it depositson metal surfaces. Slime carried through the cooling system plugs andfouls lines, valves, strainers, etc., and deposits on heat exchangesurfaces. In the latter case, the impedance of heat transfer can greatlyreduce the efficiency of the cooling system.

In pulp and paper mill systems, slime formed by microorganisms iscommonly encountered and causes fouling, plugging, or corrosion of thesystem. The slime also becomes entrained in the paper produced to causebreakouts on the paper machines, which results in work stoppages and theloss of production time. The slime is also responsible for unsightlyblemishes in the final product, which result in rejects and wastedoutput.

The previously discussed problems have resulted in the extensiveutilization of biocides in cooling water and pulp and paper millsystems. Materials which have enjoyed widespread use in suchapplications include chlorine, chlorinated phenols, organs-bromines, andvarious organo-sulfur compounds. All of these compounds are generallyuseful for this purpose but each is attended by a variety ofimpediments. For example, chlorination is limited both by its specifictoxicity for slime-forming organisms at economic levels and by thetendency of chlorine to react, which results in the expenditure of thechlorine before its full biocidal function is achieved. Other biocidesare attended by odor problems, and hazards with respect to storage, useor handling which limit their utility. To date, no one compound or typeof compound has achieved a clearly established predominance with respectto the applications discussed. Likewise, lagoons, ponds, lakes, and evenpools, either used for pleasure purposes or used for industrial purposesfor the disposal and storage of industrial wastes, become, during thewarm weather, besieged by slime due to microorganism growth andreproduction. In the case of industrial storage or disposal ofindustrial materials, the microorganisms cause additional problems whichmust be eliminated prior to the materials' use or disposal of the waste.

Naturally, economy is a major consideration with respect to all of thesebiocides. Such economic considerations attach to both the cost of thebiocide and the expense of its application. The cost performance indexof any biocide is derived from the basic cost of the material, itseffectiveness per unit of weight, the duration of its biocidal orbiostatic effect in the system treated, and the ease and frequency ofits addition to the system treated. To date, none of the commerciallyavailable biocides has exhibited a prolonged biocidal effect. Instead,their effectiveness is rapidly reduced as a result of exposure tophysical conditions such as temperature, association with ingredientscontained by the system toward which they exhibit an affinity orsubstantivity, etc., with a resultant restriction or elimination oftheir biocidal effectiveness, or by dilution.

As a consequence, the use of such biocides involves their continuous orfrequent addition to systems to be treated and their addition tomultiple points or zones in the systems to be treated. Accordingly, thecost of the biocide and the labor cost of applying it are considerable.In other instances, the difficulty of access to the zone in which slimeformation is experienced precludes the effective use of a biocide. Forexample, if in a particular system there is no access to an area atwhich slime formation occurs the biocide can only be applied at a pointwhich is upstream in the flow system. However, the physical or chemicalconditions, e.g., chemical reactivity, thermal degradation, etc., whichexist between the point at which the biocide may be added to the systemand the point at which its biocidal effect is desired render theeffective use of a biocide impossible.

Similarly, in a system experiencing relatively slow flow, such as apaper mill, if a biocide is added at the beginning of the system, itsbiocidal effect may be completely dissipated before it has reached allof the points at which this effect is desired or required. As aconsequence, the biocide must be added at multiple points, and even thena diminishing biocidal effect will be experienced between one point ofaddition to the system and the next point downstream at which thebiocides may be added. In addition to the increased cost of utilizingand maintaining multiple feed points, gross ineconomies with respect tothe cost of the biocide are experienced.

Specifically, at each point of addition, an excess of the biocide isadded to the system in order to compensate for that portion of thebiocide which will be expended in reacting with other constituentspresent in the system or experience physical changes which impair itsbiocidal activity.

SUMMARY OF THE INVENTION

The biocidal compositions of the present invention comprise, as activeingredients, 1) diiodomethyl-p-tolylsulfone (DIMPS) and 2)dodecylguanidine hydrochloride (DGH). These constituents arecommercially available. The synergistic effect obtained by combiningDIMPS and DGH has not been previously disclosed.

DETAILED DESCRIPTION OF THE INVENTION

Surprisingly, the present inventors have found that mixtures of DIMPSand DGH are especially efficacious in controlling the growth of fungalmicrobes, specifically the Trichoderma viride species. This particularspecies is a common nuisance fungal type found in industrial coolingwaters and pulping and paper making systems.

This particular species of mold is a member of the Fungi Imperfectiwhich reproduce by means of asexual spores or fragmentation of mycelium.It is commonly found on fallen timber and is a widely occurring soilorganism. Because of its ubiquitous nature, this mold continuallycontaminates open cooling systems and pulping and papermaking systems.Contamination can take the form of airborne spores or fungal mats--amass of agglomerated hyphae bound together with bacterial cells andcemented by gelatinous polysaccharide or proteinaceous material. Theslimy mass entraps other detritus, restricts water flow and heattransfer and may serve as a site for corrosion.

These fungi are able to grow in environments hostile to other lifeforms.While they are strict aerobes, Trichoderma produce both hyphae, thevegetative structure, and spores which require minimal metabolicturnover and are able to withstand harsher environmental conditions.Accordingly, by reason of demonstrated efficacy in the growth inhibitionof this particular species, one can expect similar growth inhibitionattributes when other fungi are encountered. It is also expected thatthese compositions will exhibit similar growth inhibition attributeswhen bacterial and algal species are encountered.

In accordance with the present invention, the combined DIMPS and DGHtreatment may be added to the desired aqueous system in need of biocidaltreatment, in an amount of from about 0.1 to about 200 parts of thecombined treatment to one million parts (by weight) of the aqueousmedium.. Preferably, about 5 to about 50 parts of the combined treatmentper one million parts (by weight) of the aqueous medium is added.

The combined treatment is added, for example, to cooling water systems,paper and pulp mill systems, pools, ponds, lagoons, lakes, etc., tocontrol the formation of fungal microorganisms, which may be containedby, or which may become entrained in, the system to be treated. It hasbeen found that the compositions and methods of utilization of thetreatment are efficacious in controlling the fungal organism,Trichoderma viride which may populate these systems. It is thought thatthe combined treatment composition and method of the present inventionwill also be efficacious in inhibiting and controlling all types ofaerobic microorganisms.

Surprisingly, it has been found that when the ingredients are mixed, incertain instances, the resulting mixtures possess a higher degree offungicidal activity than that of the individual ingredients comprisingthe mixture. Accordingly, it is possible to produce a highly efficaciousbiocide. Because of the enhanced activity of the mixture, the totalquantity of the biocidal treatment may be reduced. In addition, the highdegree of biocidal effectiveness which is provided by each of theingredients may be exploited without use of higher concentrations ofeach.

The following experimental data were developed. It is to be rememberedthat the following examples are to be regarded solely as beingillustrative and not as restricting the scope of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT

DIMPS and DGH were added in varying ratios and over a wide range ofconcentrations to a liquid nutrient medium which was subsequentlyinoculated with a standard volume of a suspension of the spores fromTrichoderma viride. Growth was measured by determining the amount ofradioactivity accumulated by the cells when 14C-glucose was added as thesole source of carbon in the nutrient medium. The effect of the biocidechemicals, alone and in combination, is to reduce the rate and amount of14C incorporation into the cells during incubation, as compared tocontrols not treated with the chemicals. Additions of the biocides,alone and in varying combinations and concentrations, were madeaccording to the accepted "checkerboard" technique described by M. T.Kelley and J. M. Matsen, Antimicrobial Agents and Chemotherapy. 9:440(1976). Following a two hour incubation, the amount of radioactivityincorporated in the cells was determined by counting (14C liquidscintillation procedures) for all treated and untreated samples. Thepercent reduction of each treated sample was calculated from therelationship: ##EQU1##

Plotting the % reduction of 14C level against the concentration of eachbiocide acting alone results in a dose-response curve, from which thebiocide dose necessary to achieve any given % reduction can beinterpolated.

Synergism was determined by the method of calculation described by F. C.Kull, P. C. Eisman, H. D. Sylwestrowicz and R. L. Mayer, AppliedMicrobiology 9,538 (1961) using the relationship: ##EQU2## where: ^(Q)a=quantity of compound A, acting alone, producing an end point

^(Q) b=quantity of compound B, acting alone, producing an end point

^(Q) A=quantity of compound A in mixture, producing an end point

^(Q) B=quantity of compound B in mixture, producing an end point

The end point used in the calculations is the % reduction caused by eachmixture of A and B. ^(Q) A and ^(Q) B are the individual concentrationsin the A/B mixture causing a given % reduction. ^(Q) a and ^(Q) b aredetermined by interpolation from the respective dose response curves ofA and B as those concentrations of A and B acting alone which producethe same % reduction as each specific mixture produced.

Dose-response curves for each active acting alone were determined bylinear regression analysis of the dose-response data. Data were fittedto a curve represented by the equation shown with each data set. Afterlinearizing the data, the contributions of each biocide component in thebiocide mixtures to the inhibition of radioisotope uptake weredetermined by interpolation with the dose-response curve of therespective biocide. If, for example, quantities of ^(Q) A plus ^(Q) Bare sufficient to give a 50% reduction in 14C content, ^(Q) a and ^(Q) bare those quantities of A or B acting alone, respectively, found to give50% reduction in 14C content. A synergism index (SI) is calculated foreach combination of A and B.

Where the SI is less than 1, synergism exists. Where the SI=l,additivity exists. Where SI is greater than 1, antagonism exists.

The data in the following tables come from treating Trichoderma viride,a common nuisance fungal type found in industrial cooling waters and inpulping and paper making systems, with varying ratios and concentrationsof DIMPS and DGH. Shown for each combination is the % reduction of 14Ccontent (% I), the calculated SI, and the weight ratio of DIMPS and DGH.

                  TABLE I                                                         ______________________________________                                        DIMPS vs. DGH                                                                 ppm       ppm     Ratio                                                       DIMPS.sup.1                                                                             DGH.sup.2                                                                             DIMPS:DGH     % I  SI                                       ______________________________________                                        6         0       100:0         91                                            3         0       100:0         85                                            1.5       0       100:0         73                                            0.75      0       100:0         48                                            0.38      0       100:0         26                                            0.19      0       100:0         16                                            0         10       0:100        93                                            0         5        0:100        84                                            0         2.5      0:100        58                                            0         1.25     0:100        23                                            0         0.625    0:100         8                                            0         0.313    0:100         6                                            6         10      1:1.7         99   1.97                                     3         10      1:3.3         98   1.52                                     1.5       10      1:6.7         98   1.26                                     0.75      10       1:13.2       97   1.18                                     0.38      10       1:26.3       96   1.15                                     0.19      10       1:52.6       95   1.15                                     6         5       1.2:1         98   1.53                                     3         5       1:1.7         97   1.07                                     1.5       5       1:3.3         96    0.82*                                   0.75      5       1:6.7         94    0.73*                                   0.38      5        1:13.2       92    0.69*                                   0.19      5        1:26.3       90    0.69*                                   6         2.5     2.4:1         98   1.28                                     3         2.5     1.2:1         97    0.80*                                   1.5       2.5     1:1.7         96    0.55*                                   0.75      2.5     1:3.3         86    0.59*                                   0.38      2.5     1:6.6         80    0.59*                                   0.19      2.5      1:13.2       72    0.69*                                   6         1.25    4.8:1         95   1.32                                     3         1.25    2.4:1         90    0.88*                                   1.5       1.25    1.2:1         82    0.71*                                   0.75      1.25    1:1.7         62   0.98                                     0.38      1.25    1:3.3         41   1.50                                     0.19      1.25    1:6.6         30   1.65                                     6         0.625   9.6:1         93   1.35                                     3         0.625   4.8:1         88    0.88*                                   1.5       0.625   2.4:1         78    0.70*                                   0.75      0.625   1.2:1         51   1.17                                     0.38      0.625   1:1.7         28   1.74                                     0.19      0.625   1:3.3         17   1.76                                     6         0.313   19.2:1        93   1.31                                     3         0.313   9.6:1         87    0.86*                                   1.5       0.313   4.8:1         75    0.79*                                   0.75      0.313   2.4:1         49   1.10                                     0.38      0.313   1.2:1         24   1.67                                     0.19      0.313   1:1.7         13   1.57                                     ______________________________________                                    

                  TABLE II                                                        ______________________________________                                        DIMPS vs. DGH                                                                 ppm       ppm     Ratio                                                       DIMPS.sup.1                                                                             DGH.sup.2                                                                             DIMPS:DGH     % I  SI                                       ______________________________________                                        6         0       100:0         92                                            3         0       100:0         85                                            1.5       0       100:0         59                                            0.75      0       100:0         33                                            0.38      0       100:0         10                                            0.19      0       100:0          0                                            0         10       0:100        94                                            0         5        0:100        86                                            0         2.5      0:100        57                                            0         1.25     0:100        17                                            0         0.625    0:100         0                                            0         0.313    0:100         0                                            6         10      1:1.7         99   2.05                                     3         10      1:3.3         99   1.56                                     1.5       10      1:6.7         98   1.35                                     0.75      10       1:13.2       98   1.23                                     0.38      10       1:26.3       97   1.19                                     0.19      10       1:52.6       96   1.20                                     6         5       1.2:1         98   1.57                                     3         5       1:1.7         98   1.06                                     1.5       5       1:3.3         96    0.85*                                   0.75      5       1:6.7         94    0.76*                                   0.38      5        1:13.2       93    0.71*                                   0.19      5        1:26.3       91    0.72*                                   6         2.5     2.4:1         97   1.33                                     3         2.5     1.2:1         95    0.85*                                   1.5       2.5     1:1.7         92    0.63*                                   0.75      2.5     1:3.3         87    0.56*                                   0.38      2.5     1:6.6         experimental                                                                  error                                         0.19      2.5      1:13.2       70    0.71*                                   6         1.25    4.8:1         96   1.22                                     3         1.25    2.4:1         92    0.77*                                   1.5       1.25    1.2:1         85    0.60*                                   0.75      1.25    1:1.7         67    0.70*                                   0.38      1.25    1:3.3         41   1.16                                     0.19      1.25    1:6.6         21   1.73                                     6         0.625   9.6:1         94   1.22                                     3         0.625   4.8:1         89    0.77*                                   1.5       0.625   2.4:1         69    0.81*                                   0.75      0.625   1.2:1         40   1.24                                     0.38      0.625   1:1.7         23   1.40                                     0.19      0.625   1:3.3          0   2.05                                     6         0.313   19.2:1        93   1.24                                     3         0.313   9.6:1         85    0.84*                                   1.5       0.313   4.8:1         62    0.93*                                   0.75      0.313   2.4:1         31   1.41                                     0.38      0.313   1.2:1          5   1.94                                     0.19      0.313   1:1.7          0   1.45                                     ______________________________________                                         Asterisks in the SI column indicate synergistic combinations in accordanc     with the Kull method supra, while:                                            .sup.1 indicates a product with 40% actives DIMPS and                         .sup.2 indicates a product with 33% actives DGH                          

In Tables I and II, differences seen between the replicates are due tonormal experimental variance.

In accordance with Tables I-II supra., unexpected results occurred morefrequently within the product ratios of DIMPS to DGH of from about1:26.3 to 9.6:1. Since the DIMPS product contains about 40% activebiocidal component and the DGH product contains about 33% activebiocidal component, when based on the active biocidal component,unexpected results appear more frequently within the range of activecomponent of DIMPS:DGH of about 1:21.7 to 11.6:1. At present, it is mostpreferred that any commercial product embodying the invention comprisesa weight ratio of active component of about 1:1 DIMPS:DGH.

While this invention has been described with respect to particularembodiments thereof, it is apparent that numerous other forms andmodifications of this invention will be obvious to those skilled in theart. The appended claims and this invention generally should beconstrued to cover all such obvious forms and modifications which arewithin the true spirit and scope of the present invention.

We claim:
 1. A microbial composition comprising (a)diiodomethyl-p-tolylsulfone and (b) dodecylguanidine hydrochloridewherein (a) and (b) are present in an amount synergistically effectiveto reduce the growth of fungi, the weight ratio of (a) to (b) from about1:21.7 to 11.6:1.
 2. The composition as recited in claim 1 wherein theweight ratio of (a) to (b) is about 1:1.
 3. A method for controlling thegrowth of fungi in an aqueous system which comprises adding to saidsystem a synergistically effective amount for the purpose of acomposition comprising (a) diiodomethyl-p-tolylsulfone and (b)dodecylguanidine hydrochloride, the weight ratio of (a):(b) from about1:21.7 to 11.6:1.
 4. The method as recited in claim 3 wherein the weightratio of (a):(b) is about 1:1.
 5. The method as recited in claim 3wherein said composition is added to said system in an amount of fromabout 0.1 to about 200 parts per million of said aqueous system.
 6. Themethod as recited in claim 3 wherein said aqueous system comprises acooling water system.
 7. The method as recited in claim 3 wherein saidaqueous system comprises a pulping and papermaking system.
 8. The methodof claim recited in claim 5 wherein said composition is added to saidsystem in an amount of from about 5 to about 50 parts per million ofsaid aqueous system.
 9. The method as recited in claim 3 wherein saidfungi is Trichoderma viride.